The invention relates to the technical field of connecting devices for at least one electric conductor employing, to immobilize the connected conductor, a loop-shaped connection spring.
In the above field, it is known practice to employ junction blocks such as those described in application DE-195 29 028 or printed circuit connection blocks as described in application DE-196 11 762 or alternatively in application DE-198 34 681.
According to those various documents, the connecting device comprises an insulating casing defining at least one connecting housing for an electric conductor. The device therefore comprises, in each connecting housing:
an interconnection piece provided with at least one connecting branch,
a looped connecting spring comprising in succession a bearing branch arranged on the connecting branch of the interconnection piece, an elbow connecting the bearing branch to an operating back piece, and a connection branch extending the operating back piece on the opposite side to the elbow towards the bearing branch and exhibiting a connection opening intended to accommodate the electric conductor to press it against the interconnection piece,
the compression means comprising a cam which is fitted into the connecting housing so as to be able to move in terms of rotation between a start of travel corresponding to the spring being in a relaxed state and an end of travel corresponding to the spring being in a compressed state, and which is provided with an operating lever extending at least partially out of the casing to allow the cam to be operated between the start and the end of travel and which has a cam path comprising, on the one hand, a zone known as the dead zone, through which the cam can pivot from the start of travel without acting on the spring and, on the other hand, a zone known as the active zone, following on from the dead zone, in which the cam gradually compresses the spring as it rotates towards the end of travel.
Such devices are entirely satisfactory in their function of connecting an electric conductor in a way which is electrically reliable and mechanically strong. However, the very design of the cam does not allow the cam to be given a stable position, particularly at the start and end of the travel.
Hence there has arisen a need for a novel type of connecting device which employs spring-compressing means which do not entail exerting an excessively high force in order to compress the spring and which are easier to use than the bistable rocker lever systems of the prior art, while at the same time preventing unwanted cam movements.
To this end, according to the invention, the device is essentially one which comprises means of slowing the rotation of the cam in the start-of-travel and/or end-of-travel position.
According to a preferred embodiment, the lever is situated against the casing when the cam is at the start of its travel, the spring being relaxed. Thus, the dead zone defines part of the cam travel during which it is possible for the cam and the lever to be moved without effort. This dead travel therefore allows the operating lever to be moved away from the casing so as to gain sufficient purchase to be able, comfortably and without the risk of injury on the lever, to exert the force needed to compress the spring using the cam.
According to another feature of the invention, the cam path is designed so that the cam is in a stable position at every point in the active zone. This provision of the invention therefore spares a user of the device the need to fully compress the spring in each connecting operation. Indeed, in certain situations, depending on the size of the electric conductor that is to be connected, it is not always necessary to fully compress the spring in order to engage the conductor in the connection aperture of the spring.
According to another advantageous feature of the invention, the cam has at least one test channel offering access to the connecting spring. As a preference, though this is not strictly necessary, the channel is designed to give at least one way of accessing the connecting spring when the spring is in the relaxed position corresponding to the start of cam travel. Thus, it is possible, through the test channel, to offer up a conductor element of a measurement device into contact with the spring in order, for example, to check whether or not there is electrical voltage at the spring and therefore at the interconnection piece.
According to another feature of the invention, the cam pivots through half a turn between the start and end of travel. This arrangement makes it possible, when the cam has a test channel, to use the same channel for measurements whether the cam is in the start of travel position or the end of travel position.
According to the invention, the casing and the cam are connected by a pivot link which may be produced in any appropriate way such as in the form of a through-pin for example, arranged both in a bore in the cam and in two complementary bores in the casing. The cam could also have a central bore intended to engage with a pin secured to the casing. However, according to a preferred embodiment of the invention, the cam comprises two lateral pivots intended to engage in two complementary bearings belonging to the casing. When the pivot link between the cam and the casing is produced in such a way, the slowing means then comprise at least two complementary shapings formed respectively on a pivot and on the corresponding bearing. The complementary shapings of the pivot and of the bearing are then designed to cooperate at least when the cam is in the start-of-travel position.
According to another arrangement of the invention aimed at simplifying the operations of mounting and assembling the connecting device, the insulating casing comprises two half-bodies known as the front and rear half-bodies. The front half-body therefore delimits at least one connecting housing and comprises a connecting facade in which at least one passage is formed for the conductor that is to be connected, and, on the opposite side to the facade, an opening for mounting the interconnection piece and the spring together with the cam.
The rear half-body is also intended to be fitted to the front half-body to close the connecting housing and immobilize at least the interconnection piece, the connecting spring and the cam.
This embodiment of the insulating casing makes it possible, in a very advantageous way, to install the various constituent parts of the device from the rear of the front casing, then to close the latter using the rear half-casing which then immobilizes the components of the device in the insulating casing.
To make the cam-mounting operations easier still, the front half-body defines two half-bearings for accommodating the cam pivots, each half-bearing being open towards the rear and comprising a semi-cylindrical part extended, in the opposite direction to a space for accommodating the spring, by a bearing stop which is roughly flat and tangential to the cylindrical part. The rear half-body therefore defines two half-bearings that complement the half-bearings of the front half-body to form the two bearings that accommodate the cam pivots.
Similarly, in order to allow the interconnection piece to be fitted into the connecting housing from the rear of the front half-casing, the connecting branch of the interconnection piece is roughly flat and has a width that exceeds the width of the remainder of the interconnection piece. The insulating casing therefore defines two lateral stops for reacting the forces exerted on the connecting branch by the connecting spring as it is compressed.
According to a preferred embodiment, the reaction stops are formed by flanges of the rear half-body which are intended to engage with the connecting branch as the two half-bodies of which the insulating casing is made are assembled.
The connecting device according to the invention may constitute various types of device such as, for example, an interconnection unit. To this end, the interconnection piece may be equipped with several spring-loaded connecting systems or systems for connecting miscellaneous conductor elements.
According to a preferred and not strictly necessary embodiment, the connecting device is intended to allow the quick connecting of electrical conductors such as electrical cables to a printed circuit board. The interconnection piece therefore comprises a stalk extending out from the casing for connection to the printed circuit.
According to a preferred embodiment, the stalk extends roughly at right angles to the connecting branch and is connected to the connecting branch by a linking branch which, as it extends from the connecting branch, is first of all bent against the connecting branch, then moves away from the connecting branch to define a stop for an electrical cable engaged in the connecting housing.
According to another feature of the invention, the casing comprises a measurement channel offering access to the interconnection piece.
According to another feature of the invention, the connecting branch of the interconnection piece has, at the opposite end to its free end, an interconnection aperture and the casing has an interconnection channel for fitting an interconnection plug into the interconnection aperture.